If you think have a shot at promotion or will be in a fight to avoid relegation, always advise to focus on league games. Lots of managers come over from HT. BB is different in that there's much more reward for promoting/avoiding relegation (yes, even with the economy changes this season).
In your case, 3 games up in the league, you might be able to afford a loss in going for a cup win. But, still want to maintain as high enthusiasm as possible for the playoffs. A CT now could effect your enthusiasm even half a season away unless you can afford to TIE at least one league game a week.
"Well, no ones gonna top that." - http://tinyurl.com/noigttt